Camshafts are used to control the gas exchange valves in internal combustion engines. In a four-cycle engine, the camshafts rotate at half the engine speed. The control elements used to move the gas exchange valves are cams consisting of base circle areas and radially elevated or lobed areas. An end piece to receive the chain wheel or gear wheel or a sensor wheel and other elements may be additionally provided, for example, on the camshaft.
In accordance with their function the cams on the camshaft are mounted offset in the longitudinal axis. As a result, the camshaft as a whole is imbalanced, which can lead to additional undesirable engine vibrations at least in certain speed ranges.
Furthermore, all the rotating masses of the engine cause vibrations. At least some of these vibration phenomena can be compensated in practice by installing counter-imbalances. These counter-imbalances can be balancing weights on the camshaft, and/or so-called balancer shafts can be provided specifically for this purpose.
Published German patent application nos. DE 40 30 568 C2 and DE 43 36 809 C2 describe the use of balancing weights in camshafts. In one embodiment of DE 40 30 568 C2, balancing masses are eccentrically offset relative to the axis of rotation to compensate imbalances in a solid camshaft. In another embodiment, balancing masses in the form of tubular sections are likewise eccentrically offset relative to the axis of rotation. Such shafts are expensive to manufacture and have limited application.
DE 43 36 809 C2 proposes that cams mounted to the shaft be provided with a bore and mounted to a basic shaft body. On the side of the cam opposite the cam lobe the cams have a balancing mass in the form of a projection configured as an axial extension, namely a half shell integrally formed with the cam. Such camshafts again have limited application because the position of the cams and the balancing weight must be defined in advance in relation to each other and cannot be varied.